Airplanes generally are equipped with several hydraulic circuits, allowing activation of all the ancillary equipment of the airplane. Generally, each device controlled by a hydraulic circuit is installed on both a main hydraulic circuit and an auxiliary hydraulic circuit, independent and autonomous, for reasons of safety.
As described in the document FR 2 888 898, it is known to use on such a hydraulic system an energy reserve accumulator that makes it possible to release its hydraulic energy reserve to the controlled components, in order to maintain the pressure in the hydraulic circuit at a level close to the rated operating pressure of these components. This energy reserve accumulator is placed on the high-pressure hydraulic line of the fluid system, between a hydraulic power generator and the controlled components, remote from the hydraulic power generator. Such an accumulator makes it possible to absorb the-overpressures generated in the hydraulic circuit by the operation of the various controlled components, and in this way to prevent the structure and the equipment items of the airplane from being damaged during sudden pressure change in the lines.
In order to monitor the status of an energy reserve accumulator, the document FR 2 888 898 proposes a method for checking the status of pressurization of an energy accumulator. In principle, this monitoring method consists, after having pressurized the fluid system to an operating pressure, of measuring the time interval necessary for the fluid system to progress from a predetermined first pressure to a predetermined second pressure and in comparing this time interval with a predetermined reference time. The predetermined reference time is determined by using the monitoring method on a reference accumulator.
The monitoring method in FR 2 888 898, however, is ineffective in certain configurations of the hydraulic system. In fact, the speed with which the pressure of the fluid decreases in a fluid system depends on the voluminal capacity of this system. Thus, the greater the volume of fluid, the longer the pressure of the fluid system will take to drop. Furthermore, in a fluid system, there is an internal flow between the high-pressure part and the low-pressure part of the system. The lower the flow between the high-pressure part and the low-pressure part, the longer the pressure of the system will take to drop.
Thus, in an aircraft with low flow rate or with a large voluminal capacity of the fluid system, the time taken by the system to progress from a first predetermined pressure to a second predetermined pressure may be considerable because of the configuration of the hydraulic system itself, and thus is not directly representative of the operating status of the energy accumulator.